MAIL
About this task
In conversations mode, the most recent reply in a conversation is displayed in the message list, and any other replies and the original message are collapsed below the most recent reply. When you expand the conversation, the original message displays its subject, and each reply displays its first line of text.
Procedure
To enable or disable conversations, click Show -> Conversations or Show -> Individual Messages.
Note: Conversations can be viewed and sorted by Date only. Sorting by another column, such as Sender, automatically switches the view or folder back to messages mode.
Parent topic: Personalizing your Mail settings